On Sat, 2009-10-03 at 16:51 +0200, Andreas Schwab wrote: > Andreas Schwab <sch...@linux-m68k.org> writes: > > > Andreas Schwab <sch...@linux-m68k.org> writes: > > > >> Anton Blanchard <an...@samba.org> writes: > >> > >>> On 64bit applications the VDSO is the only thing in segment 0. Since the > >>> VDSO > >>> is position independent we can remove the hint and let get_unmapped_area > >>> pick > >>> an area. > >> > >> This breaks gdb. The section table in the VDSO image when mapped into > >> the process no longer contains meaningful values, and gdb rejects it. > > > > The problem is that the load segment requires 64k alignment, but the > > page allocater of course only provides PAGE_SIZE alignment, causing the > > image to be unaligned in memory. > > Here is a patch. The disadvantage is that now gdb complains that the > vdso does not contain section headers, because they are no longer > covered by the load segment.
Maybe a better fix is to force alignment in the kernel by requesting size + 64k - 4k and aligning it. Ben. > Andreas. > --- > >From 003c323c753d8717e58220c9560329882bcfa2c2 Mon Sep 17 00:00:00 2001 > From: Andreas Schwab <sch...@linux-m68k.org> > Date: Sat, 3 Oct 2009 16:46:45 +0200 > Subject: [PATCH] powerpc: fix unaligned load segment in vdso64 > > Since the page allocator can only guarantee PAGE_SIZE alignment the load > segment in the vdso object cannot claim more than that alignment. Use 4k > alignment which is the minimum possible page size. > > Signed-off-by: Andreas Schwab <sch...@linux-m68k.org> > --- > arch/powerpc/kernel/vdso64/Makefile | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/arch/powerpc/kernel/vdso64/Makefile > b/arch/powerpc/kernel/vdso64/Makefile > index 79da65d..d4be303 100644 > --- a/arch/powerpc/kernel/vdso64/Makefile > +++ b/arch/powerpc/kernel/vdso64/Makefile > @@ -10,7 +10,9 @@ obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64)) > GCOV_PROFILE := n > > EXTRA_CFLAGS := -shared -fno-common -fno-builtin > +# Force maximum page size of 4k so that it works with any page size > EXTRA_CFLAGS += -nostdlib -Wl,-soname=linux-vdso64.so.1 \ > + -Wl,-z,max-page-size=4096 \ > $(call cc-ldoption, -Wl$(comma)--hash-style=sysv) > EXTRA_AFLAGS := -D__VDSO64__ -s > > -- > 1.6.4.4 > > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
